Rotor and Stator Maintenance: Ensuring Optimal Performance

Rotor Certificate: Key Inspection Points

1. Shaft and Polar Icecaps: Carefully inspect the shaft and polar icecaps for any cracks or signs of oxidation.
2. Shaft Pads: The shaft pads on the bearings should exhibit a smooth surface and no signs of excessive wear on the slip rings.
3. Slip Ring Cleaning: Clean the slip rings with a cloth soaked in alcohol. They should appear smooth and shiny. If sparking, roughness, or excessive wear is observed, the slip rings should be inspected using a lathe.
4. Induction Coil Resistance:
   • Using an ohmmeter, measure the resistance of the induction coil.
   • Apply the probes to the slip rings. The reading should match the manufacturer's recommended value (typically 4 to 5 ohms as a guideline).
   • Measure the insulation of the induction coil with respect to ground. Apply one end of the ohmmeter to one of the slip rings and the other end to the rotor shaft. This should yield an infinite resistance reading.

Troubleshooting Rotor Issues

• If the obtained resistance value is lower than the manufacturer's specification, it indicates a short circuit between turns.
• If the resistance is higher than expected, it suggests a faulty connection between the coil and the slip rings.
• If the ohmmeter shows no reading (infinite resistance), it means the coil is cut.

If any of these anomalies are detected, the entire rotor should be replaced, as any repair attempts may negatively impact the machine's performance.

Stator Inspection: Ensuring Optimal Condition

1. Stator Windings: Verify that the stator windings are in good condition, without any malformation or deterioration in the insulation. Use an ohmmeter for this inspection.
2. Insulation Testing: Using an ohmmeter, check the insulation between each of the phases (coils) and the mass (housing).
3. Phase Resistance: Measure the resistance between each phase using an ohmmeter. The reading should match the manufacturer's recommendation (typically 0.2 to 0.35 ohms, depending on the winding connection - star or triangle). The measurements should be equal between phases. An infinite resistance reading indicates that the winding is cut.

Brush Inspection: Maintaining Proper Contact

• Ensure that the brushes move smoothly within the support housing and that the outlet cable is not broken or detached from the brush.
• Verify that the brushes sit perfectly on the slip rings and that their length exceeds 10 mm. If the length is less than 10 mm, replace the brush set.
• Using a multimeter, check the continuity between the terminal of the electric brush holder and the brush. Additionally, check the isolation between the two with respect to ground.